What is the best topic sentence for an article about whether or not certain genes play a favorable role in human evolution?

"jumping genes," or transposable elements, are dna sequences that have the ability to replicate and move from one chromosome to another.
nobel laureate barbara mcclintock first reported this phenomenon in 1951, but few other scientists believed her findings at the time.
jumping genes have the unsavory reputation of causing genetic mutation or cancerous cell growth.
challenging the notion that jumping genes are "junk" genes, recent b

Why are small quantities of chlorofluorocarbons so harmful to the ozone layer? a. the chlorofluorocarbons act like ultraviolet radiation causing large amount of ozone to be produced. b. the chlorine from the chlorofluorocarbons reacts with free molecules of oxygen causing a stop in ozone production c. free oxygen atoms can replace the chlorine in chlorine monoxide, releasing a free atom of chlorine which can then recombine with an oxygen atom in ozone, destroying more ozone. d. chlorofluorocarbons absorb ultraviolet radiation, preventing the formation of ozone select the best answer from the choices provided

Tlymphocytes mature in the? a. thyroid gland. b. bone marrow. c. spleen. d. thymus.

What element does susan b. anthony include in this passage to strengthen her argument?